In a manufacturing process for manufacturing semiconductor devices, liquid crystal panels, LEDs, solar cells or the like, a process gas is introduced into a process chamber which is being evacuated to perform various processes such as an etching process, a CVD process or the like. The process chamber for performing several processes such as an etching process, a CVD process or the like is evacuated by a vacuum pump. Further, the process chamber and exhaust apparatuses connected to the process chamber are cleaned periodically by supplying a cleaning gas thereto. Because exhaust gases such as the process gas, the cleaning gas or the like contain a silane-based gas (SiH4, TEOS or the like), a halogen-based gas (NF3, ClF3, SF6, CHF3 or the like), a PFC gas (CF4, C2F6 or the like) or the like, such exhaust gases have negative effects on the human member and on the global environment such as global warming. Therefore, it is not preferable that these exhaust gases are emitted to the atmosphere as they are. Accordingly, these exhaust gases are made harmless by an exhaust gas treatment apparatus provided at a downstream side of the vacuum pump, and the harmless exhaust gases are emitted to the atmosphere.
Heretofore, the vacuum pump and the exhaust gas treatment apparatus are housed respectively in individual housings, and hence they are installed in distant positions and connected to each other by a long pipe. Thus, the vacuum pump and the exhaust gas treatment apparatus have not been an optimum system from the standpoint of saving energy by interchanging necessary heat between the vacuum pump and the exhaust gas treatment apparatus. Therefore, a system comprising a vacuum pump and an exhaust gas treatment apparatus which are accommodated in one housing and connected by a short pipe has been developed, and such system has been sold as an integrated-type exhaust system. However, even in such integrated-type exhaust system, the pipe interconnecting the vacuum pump and the exhaust gas treatment apparatus is several meters long, and is kept warm or heated by a heater or the like for preventing a product generated by gas treatment from being attached to the pipe.
In both of the exhaust system wherein the vacuum pump and the exhaust gas treatment apparatus are housed respectively in individual housings and the exhaust system wherein the vacuum pump and the exhaust gas treatment apparatus are housed in one housing, the conventional exhaust gas treatment apparatuses have the following problems:
1) The exhaust gas treatment apparatus employs a premixing burner for premixing a fuel and oxygen and combusting a mixture to generate high-temperature fames for treating an exhaust gas to allowable concentration (TLV: a threshold limit value) or smaller with a small amount of fuel. Therefore, the exhaust gas treatment apparatus requires pure oxygen as a utility.
2) Although the exhaust gas treatment apparatus has a high gas treatment performance by high-temperature flames, a product generated by the gas treatment is melted and solidified, and the melted and solidified product is attached to an interior of a combustor. Therefore, a maintenance periodic cycle becomes short.
3) The exhaust gas treatment apparatus has single-stage swirling air supply nozzles configured primarily to form swirling flows of air in the combustor. The swirling air does not have any other functions.
4) Since the exhaust gas to be treated is combusted in the vicinity of the flames with the exhaust gas retaining a high concentration, the melted and solidified product is liable to be attached to the interior of the combustor. Although the attached product is removed by a scraper, the product that has not removed but has remained is accumulated in the combustor, thus requiring maintenance of the interior of the combustor in a certain periodic cycle.
5) The inflow direction of the exhaust gas to be treated into the combustor and the inflow direction of the swirling air into the combustor are perpendicular to each other to increase the agitation efficiency of the gases in the combustor, thereby efficiently supplying oxygen to the exhaust gas to be treated to combust the exhaust gas quickly in the vicinity of the flames for a high treatment performance. However, the melted product is liable to be attached to the inner surface of the combustor near the flames.
6) The inflow direction of the exhaust gas to be treated is fixed, and the treatment performance is adjusted mainly by art increase or decrease of the fuel.
7) A powder that has been produced by treating the exhaust gas is collected in a tank. When a certain amount of powder is accumulated in the tank, maintenance of the tank is performed to remove the powder or the powder is discharged from the tank with water.
8) The exhaust gas treatment apparatus is purged at all times by a small flow rate of air or nitrogen.
9) After the exhaust gas is combusted and treated, the produced combustion gas is cooled by contact with water.